There are a few reflections on the skull, from text on glass partitions that keep the fossils safe. I tried to edit the picture to make them less obvious.

This is AMNH 3856, a cast (according to the label) received in exchange from Tübingen. I guess it and some ichtyosaurs are the exchange objects for the Diplodocus material that founds its way to Tübingen. The skull was sculpted very skillfully by Elliot Goldfinger.